1982 CB750F...Better Devil
- Thread starter Jimbonaut
- Start date
pidjones
Over 1,000 Posts
There is a great CB750 carb rebuild procedure pdf by SeanG on cb750c.com: http://www.cb750c.com/publicdocs/SeanG/Honda_Carb_Manual_revG.pdf (don't know if a direct link works, but you can try). It stresses thorough cleaning of the slow speed jets and pilot circuit. My accelerator jets were plugged solid, eve with sonication and carb cleaner under pressure. I ended up with the finest guitar string I had (high G from a 12 string) in a pin vice to reach from the outlet end with butterfly open and finally hit the tiny hole to clear it, then a liberal flush of carb cleaner. But, mine had been sitting since 1999. I also had to solder up two of my overflow tubes due to cracks. I made a temp fuel supply with 91% isopropyl alcohol for leak testing. Less stink, evaporates well, mixes and burns if any is left. To test for cracked overflow tubes, fill each with alcohol over a sink with the bowl drain closed. Nothing should come out the drain. If it does, inspect carefully for a crack running up the tube. I soldered mine.
i just drill the tubes out and press in new ones
i had to fix 8 float bowls last week
when checking for leaks have a look at the tip of the drain screws with our
wonderful ethanol fuel the water in the carb goes to the lowest point in the bowl
right around the tip of the screw and eats the screw sometimes causing a leak if its disturbed
the factory screws are steel and get corroded
i use brass drain screws when i replace them that i get from sirius sonic inc
https://www.siriusconinc.com/pro-detail.php?pid=&product_id=1371
they seal up great never stick either
i had to fix 8 float bowls last week
when checking for leaks have a look at the tip of the drain screws with our
wonderful ethanol fuel the water in the carb goes to the lowest point in the bowl
right around the tip of the screw and eats the screw sometimes causing a leak if its disturbed
the factory screws are steel and get corroded
i use brass drain screws when i replace them that i get from sirius sonic inc
https://www.siriusconinc.com/pro-detail.php?pid=&product_id=1371
they seal up great never stick either
Thanks guys, that's really great info. I have some drain screws on order and already have rebuild kits for the carbs - I've emailed Sean to see if he he still has o rings and screw sets. That's a helluva walk-thru pidjones, many thanks for the link. Invaluable, and a great companion to the Mike Nixon booklet I have. Thanks again gents.
Lots of good stuff showing up recently (thanks in no small part to Maritime, thanks mate - owe you so many beers now) -
- carb and piston parts, engine gaskets, bolts and oil seals, cam chain tensioner, valve cover bolt seals and caliper rebuild kits. Also picked up my freshly powder coated frame and calipers -
- chose an old bronze, slightly metallic colour - snazzy. Gloss black for the frame - I've powder coated a few frames now but have to say the gloss black really is something. Guess there's a good reason it's the go-to. No photos (everything's still glad-wrapped) but I'll get some up soon.
Also picked up a bunch of parts and engine covers from glass bead cleaning -
- thing's look brand new. First time for me, but won't be the last. To think I spent weeks (literally) cleaning and sanding these things on my last CB to get them to a state not even half this good - glass bead for the win. More snazz.
- carb and piston parts, engine gaskets, bolts and oil seals, cam chain tensioner, valve cover bolt seals and caliper rebuild kits. Also picked up my freshly powder coated frame and calipers -
- chose an old bronze, slightly metallic colour - snazzy. Gloss black for the frame - I've powder coated a few frames now but have to say the gloss black really is something. Guess there's a good reason it's the go-to. No photos (everything's still glad-wrapped) but I'll get some up soon.
Also picked up a bunch of parts and engine covers from glass bead cleaning -
- thing's look brand new. First time for me, but won't be the last. To think I spent weeks (literally) cleaning and sanding these things on my last CB to get them to a state not even half this good - glass bead for the win. More snazz.
Looking good Jim. Blasting is definitely the way to go, hand cleaning one air cooled engine was more than enough for me. Are you going to paint the engine bits?
I have yet to get any cool colors of powder, but its on the list.
I have yet to get any cool colors of powder, but its on the list.
Plan is to polish the engine covers, lump itself will be satin black with polished fins.
You got any idea what grade sandpaper I should start with? I'm thinking pretty high (hopefully) as I don't want to create any more work for myself than necessary. Obvs.
As the entire brake system is going to be essentially brand new, I'm going to use DOT 5 which apparently won't bugger up paint/powder when I predictably spill it all over the bike.
You got any idea what grade sandpaper I should start with? I'm thinking pretty high (hopefully) as I don't want to create any more work for myself than necessary. Obvs.
As the entire brake system is going to be essentially brand new, I'm going to use DOT 5 which apparently won't bugger up paint/powder when I predictably spill it all over the bike.
Jimbonaut said:
Let me know how the powder holds up. I'm going to powdercoat the brake backing plates for the bus and was worried about that.
Try polishing the blasted surface and see how it comes out. You may get lucky.
Will do. Not too worried about damaging the powder with the brake fluid, but wondering how it'll hold up against the heat. I'll let you know mate. If I can get away with polishing the covers without any sanding then I'm in like Flynn. One way to find out.
Jimbonaut said:
I think that ship already sailed. most media blasting will make make the surface textured and take more elbow grease to get out. I would start will 220 and go from there. It usually saves time to start fairly low and work your way up in as small of steps as possible, working in a crosshatch pattern.
Or alternatively if you have a buffer with some good torque, you can take it to 320 and get a pretty good polish with the right mix of wheels and rouge, the high speed buffers kind of "melt" the surface on aluminum so you don't have to polish very high to get a good finish.
CarbsAndCylinders
Careful With That Axe Eugene
Looks great but I particularly like the way the calipers turned out. 
Cheers mate - I nearly powdered the whole frame that colour but bottled it. The tank'll have some colour too it and at the 25 hour I though it might all be a bit too much. But yeah, colour looks pretty sweet on the calipers, and definitely very happy to hear about DOT 5 not damaging painted or powdered surfaces.
Aye, I think somewhere in the back of my mind that was the swing vote Mike.
Going back to the DOT 5 thing, the Nissan master cylinder I'm looking at makes a big song and dance about how it's not compatible with DOT 5 fluid, but I can't find much evidence or reasoning to back this up. Is it just a throw-back to some bygone era that simply poo-poo's anything but DOT 3 or 4 (I think any master cylinder I've seen all have something like "use only DOT 3 or DOT 4 from a sealed container" written on the lid) being used? Is there a reason for saying DOT 5 is not compatible - might it effect the rubber seals in the master cylinder? Or is it something more nefarious - master cylinder manufacturers wanting us to use DOT 3 or DOT 4 so the seals do wear out and therefore force us to buy new parts? Or is that just cynical?
Going back to the DOT 5 thing, the Nissan master cylinder I'm looking at makes a big song and dance about how it's not compatible with DOT 5 fluid, but I can't find much evidence or reasoning to back this up. Is it just a throw-back to some bygone era that simply poo-poo's anything but DOT 3 or 4 (I think any master cylinder I've seen all have something like "use only DOT 3 or DOT 4 from a sealed container" written on the lid) being used? Is there a reason for saying DOT 5 is not compatible - might it effect the rubber seals in the master cylinder? Or is it something more nefarious - master cylinder manufacturers wanting us to use DOT 3 or DOT 4 so the seals do wear out and therefore force us to buy new parts? Or is that just cynical?
Maritime
Over 10,000 Posts
IDK re DOT 5 vs 4 vs 3 but it could be as simple as when that master was produced it wasnt testes on 5 or 5 wasnt around. My mid eighties cbr600 says DOT 3 only, but the other fluids were not available so maybe I can use 5. Rumor has it you can put the newer stuff in older systems but not the other way around. Ive not found a trusted source on that yet. I think Irk has a reference on it that may confirm.
Maritime
Over 10,000 Posts
Quick google: http://collision.alldata.com/online2help/shopOps/Inspection_Forms,_System_Checklists_and_Customer_Questions/Answers_to_Common_Customer_Questions/Brakes/can_dot_5_brake_fluid_be_used_instead_of_dot_3_or_41.htm
I didnt vet the source but sounds legit and I think its what Irk said in an earlier post. Hes smart enough to trust most of the time ;D
I didnt vet the source but sounds legit and I think its what Irk said in an earlier post. Hes smart enough to trust most of the time ;D